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, 25 (5), 262-268

Systematic Analysis of Translocator Protein 18 kDa (TSPO) Ligands on Toll-like Receptors-mediated Pro-inflammatory Responses in Microglia and Astrocytes

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Systematic Analysis of Translocator Protein 18 kDa (TSPO) Ligands on Toll-like Receptors-mediated Pro-inflammatory Responses in Microglia and Astrocytes

Ji-Won Lee et al. Exp Neurobiol.

Abstract

Translocator protein 18 kDa (TSPO) is a mitochondrial protein highly expressed on reactive microglia and astrocytes, and is considered as a biomarker for neurodegeneration and brain damage, especially neuroinflammation. Toll-like receptors (TLRs) are closely related with inflammatory responses of microglia and astrocytes and these signaling pathways regulate neuroinflammation. Previous reports have identified the anti-inflammatory effects of TSPO ligands, however study of their effects in relation to the TLR signaling was limited. Here, we investigated the effects of five representative TSPO ligands on microglia and astrocytes following activation by various TLR ligands. Our results show that TSPO ligands reduce the pro-inflammatory response elicited by the TLR ligands with more profound effects on microglia than astrocytes.

Keywords: TSPO; TSPO ligands; Toll-like receptors; astrocyte; microglia.

Figures

Fig. 1
Fig. 1. The comparative analyses of the TLR ligands-induced secretion of pro-inflammatory cytokines and TSPO expression levels in microglia and astrocytes. Immunocytochemistry images of microglia (A) and astrocytes (G). ELISA of TNF-α (B, H), IL-6 (C, I) and CCL2 (D, J) were performed in the supernatants from the microglia and astrocytes 24 h after the TLR ligands stimulation. Immunoblot analysis of TSPO in the lysates of microglia (F) and astrocytes (L). Quantitative analysis of TSPO protein levels was performed after normalization to β-actin. All data are presented as mean±SEM. *p<0.05, **p<0.01 and ***p<0.001 versus control (Con). Immuno blot data are representative of at least three independent experiments.
Fig. 2
Fig. 2. TSPO ligands have no cytotoxic effects on microglia and astrocytes. (A) The table presents the class, name (and alternative name) and chemical structure of TSPO ligands. Microglia (B) and astrocytes (C) were treated with 50 µM of etifoxine, FGIN-1-27, PK11195, Ro5-4864, or XBD-173 for 24 h, and cell death assay was performed to assess the cytotoxicity of the TSPO ligands.
Fig. 3
Fig. 3. TSPO ligands suppress production of the TLR ligands-induced pro-inflammatory cytokines in microglia. ELISA of TNF-α (A, B), IL-6 (C, D) and CCL2 (E, F) from Pam3CSK4 or LPS-stimulated microglia with pre-treatment with 50 µM of etifoxine, FGIN-1-27, PK11195, Ro5-4864, or XBD-173. Cultured media were collected and TNF-α (G), IL-6 (H) and CCL2 (I) were measured by ELISA after stimulation with other TLR ligands with pretreatment with etifoxine or PK11195. TNF-α and IL-6 were measured at 12 h and CCL2 was analyzed at 24 h after stimulation, respectively. Data are presented as mean±SEM. *p<0.05, **p<0.01 and ***p<0.001 versus TLR ligand alone, respectively.
Fig. 4
Fig. 4. TSPO ligands suppress production of the TLR ligands-induced pro-inflammatory cytokines in astrocytes. ELISA of TNF-α (A, B), IL-6 (C, D) and CCL2 (E, F) from Pam3CSK4 or LPS-stimulated astrocytes with pre-treatment with 50 µM of etifoxine, FGIN-1-27, PK11195, Ro5-4864, or XBD-173. Culture media were collected and TNF-α (G), IL-6 (H) and CCL2 (I) were measured by ELISA after stimulation with other TLR ligands with pretreatment with etifoxine or PK11195. TNF-α and IL-6 were measured at 12 h and CCL2 was measured at 24 h after stimulation, respectively. Data are presented as mean±SEM. *p<0.05, **p<0.01 and ***p<0.001 versus TLR ligand alone, respectively.
Fig. 5
Fig. 5. Summary of the inhibitory effects of TSPO ligands on TLR ligands-induced pro-inflammatory responses in microglia and astrocytes.

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References

    1. Papadopoulos V, Baraldi M, Guilarte TR, Knudsen TB, Lacapère JJ, Lindemann P, Norenberg MD, Nutt D, Weizman A, Zhang MR, Gavish M. Translocator protein (18kDa): new nomenclature for the peripheral-type benzodiazepine receptor based on its structure and molecular function. Trends Pharmacol Sci. 2006;27:402–409. - PubMed
    1. Veiga S, Carrero P, Pernia O, Azcoitia I, Garcia-Segura LM. Translocator protein 18 kDa is involved in the regulation of reactive gliosis. Glia. 2007;55:1426–1436. - PubMed
    1. Rupprecht R, Papadopoulos V, Rammes G, Baghai TC, Fan J, Akula N, Groyer G, Adams D, Schumacher M. Translocator protein (18 kDa) (TSPO) as a therapeutic target for neurological and psychiatric disorders. Nat Rev Drug Discov. 2010;9:971–988. - PubMed
    1. Daugherty DJ, Chechneva O, Mayrhofer F, Deng W. The hGFAP-driven conditional TSPO knockout is protective in a mouse model of multiple sclerosis. Sci Rep. 2016;6:22556. - PMC - PubMed
    1. Bae KR, Shim HJ, Balu D, Kim SR, Yu SW. Translocator protein 18 kDa negatively regulates inflammation in microglia. J Neuroimmune Pharmacol. 2014;9:424–437. - PubMed
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